1. Field of the Invention
One aspect of the present invention generally relates to a catalytic converter, and more specifically, to a support seal for a catalytic converter.
2. Background Art
Catalytic converters are utilized in vehicles for reacting with hot vehicle exhaust gases and for purifying such gases. The catalytic converter typically includes a substrate, often times referred to as a brick. The substrate is often constructed of a ceramic material. The substrate may include channels or other fluid conduits, such as honeycombs, for the passage of the hot exhaust gases. A catalyst is added to the substrate for carrying out the catalytic function.
The catalytic converter also includes a housing having a chamber, an inlet for receiving gas, and an outlet for exhausting gas. In many applications, the brick is positioned within the chamber for performing the gas purifying function. A support member, for example, a mat or a wire mesh, is often wrapped around the substrate for supporting the brick with respect to the housing. As non-limiting examples, the mat can be made from intumescent or non-intumescent material. An example of an intumescent material is the INTERAM product, available from 3M of Minneapolis, Minn. The wire mesh can be made from stainless steel wire drawn from rod which is woven or knitted. The substrate support member which is placed between the substrate and the shell exerts pressure radially to hold the substrate in place. This pressure prevents the substrate from movement, thus preventing damage during service. The support member can also absorb shock caused when the vehicle is driven over uneven road surfaces, for example pot holes or dirt roads.
In certain circumstances, when a wire mesh type support member is used, the support member does not effectively limit the leakage of untreated gas through the catalytic converter chamber. As such, seals have been utilized to reduce the leak rates to tolerable levels. A seal is commonly fixed to the inlet and/outlet ends of the chamber and is disposed between the substrate and the chamber. In many applications, these seals can be particularly effective and economical for use with catalytic converters. The seal compensates for surface irregularities and/or voids on or between the substrate and/or chamber caused by the flexibility of the support member. The seal can be constructed of wire such that it can withstand relatively high temperatures typical of the catalytic converter environment. Knitted wire elements can be used as the seals. The seal sometimes can be covered with fiberglass fabric. Filler materials can also be added to reduce leakage rates.
One proposal provides a seal with a V-shaped configuration. The seal can be formed such that the apex of the V-shape is disposed on one side of the seal and the legs of the V-shape diverge from the apex to define interior and exterior surfaces of the seal. The legs of the seal can have an angle of divergence of about 60 degrees for substantially the entire length of the seal.
Current catalytic converters with or without seals are designed such that there is some space left on either side of the substrate along the length of the inside surface of the chamber. As such, the substrate is held in place by forces generated by the support member around the surface of the substrate in a radial direction only. As a result, the brick can experience movement in the axial direction when the radially restraining force level deteriorates over a period of time in use. This radial movement of the brick can be detrimental to the brick, and may eventually cause brick failure.
In light of the foregoing, what is needed is a support seal for providing support in the axial direction of a catalytic converter housing. What is also needed is a catalytic converter having a support seal with a mechanical design with relative high durability and/or robustness.